JP2004303281A - Polishing pad, manufacturing method of information recording medium glass substrate using above pad and information recording medium glass substrate obtained by above method - Google Patents

Polishing pad, manufacturing method of information recording medium glass substrate using above pad and information recording medium glass substrate obtained by above method Download PDF

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JP2004303281A
JP2004303281A JP2003091125A JP2003091125A JP2004303281A JP 2004303281 A JP2004303281 A JP 2004303281A JP 2003091125 A JP2003091125 A JP 2003091125A JP 2003091125 A JP2003091125 A JP 2003091125A JP 2004303281 A JP2004303281 A JP 2004303281A
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polishing
glass substrate
information recording
pad
glass
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JP4790973B2 (en
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Yozo Nakano
洋三 中野
Yoichi Tajima
洋一 田島
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Nippon Sheet Glass Co Ltd
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Nippon Sheet Glass Co Ltd
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Priority to JP2003091125A priority Critical patent/JP4790973B2/en
Priority to US10/807,670 priority patent/US6932677B2/en
Publication of JP2004303281A publication Critical patent/JP2004303281A/en
Priority to US11/182,296 priority patent/US7059951B2/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/07—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool
    • B24B37/08—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for double side lapping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/11—Lapping tools
    • B24B37/20—Lapping pads for working plane surfaces
    • B24B37/24—Lapping pads for working plane surfaces characterised by the composition or properties of the pad materials

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Magnetic Record Carriers (AREA)
  • Grinding-Machine Dressing And Accessory Apparatuses (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)
  • Manufacturing Optical Record Carriers (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad in which amount of production of information recording medium glass substrates is improved while maintaining stable quality and yield of the products, to provide a manufacturing method of the substrates using the pad and to provide the substrates obtained by the method. <P>SOLUTION: The substrates are manufactured by roughly grinding the surface of glass material and then, precision polishing is conducted using the polishing pad. The pad is provided with a base stock and a polishing section which is laminated on the base stock and contacts with the surface of the glass material during polishing. The polishing section of the pad is formed by a foamed body whose material is synthetic resin having 100% modulus defined by JIS K7113 that is equal to or less than 11.8 MPa (120 kgf/cm<SP>2</SP>) and a maximum height of the surface (Rmax) set by JIS B0601-1982 is equal to or less than 70 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、例えばハードディスク等のような情報記録装置の磁気記録媒体である磁気ディスク、光磁気ディスク、光ディスク等の情報記録媒体の製造時に使用する研磨パッド及びそれを使用した情報記録媒体用ガラス基板の製造方法並びにその方法で得られた情報記録媒体用ガラス基板に関するものである。
【０００２】
【従来の技術】
従来、上記のような情報記録媒体の１つである磁気ディスクは、ハードディスク装置等に内装されて使用されている。同磁気ディスクは、情報記録媒体用ガラス基板（以下、略して「ガラス基板」とも記載する）の表面に磁性層等を積層することによって製造される。また、磁気ディスクに記録された磁気記録情報を読み取るための磁気ヘッド（以下、略して「ヘッド」とも記載する）は、磁気ディスクに対してその表面から浮上した状態で移動するように構成されている。
【０００３】
当該ヘッドが移動するときに磁気ディスクの表面に凹凸が存在すると、これら凹凸とヘッドとが衝突し、ヘッドの損傷、磁気ディスクの傷つき等のような不具合を生じるおそれがある。さらに、近年の磁気ディスクには記録容量の増大が求められており、これに応えるには磁気ディスクの表面とヘッドとの距離を極力狭めて記録密度を高める必要がある。そこで、磁気ディスクに使用されるガラス基板は製造時に研磨処理を施されており、表面の平坦度を向上させて表面凹凸の発生を抑える試みがなされている。（例えば、特許文献１参照。）。当該研磨処理では、研磨用キャリア及び研磨パッドを備える研磨装置が使用される。そして、研磨処理時には、研磨用キャリアにガラス基板を収容した状態でガラス基板の表面に研磨パッドを接触させ、ガラス基板及び研磨パッドを互いに回転させることにより、ガラス基板の表面が研磨される。
【０００４】
【特許文献１】
特開２０００−２８８９２２号公報
【０００５】
【発明が解決しようとする課題】
ところで、上記の研磨パッドは、これを使用して製造されたガラス基板が所望とする品質を満たさなくなったとき、耐用限界とみなされて新たな研磨パッドに交換される。従来の研磨パッドは、ＳＲＩＳ−０１０１に規定されるアスカーＣ硬度を基準に、研磨用キャリアの硬さ、ガラス材料の硬さ等といった目的に対応した硬さのものを選択し、これに応じてガラス基板に求められる品質、研磨パッドの交換時期等が決められていた。この研磨パッドは、不織布等よりなる基材と、同基材の表面に積層され、ガラス基板の表面に接触されることとなる合成樹脂製の発泡体よりなる研磨部とで構成されている。しかし、アスカーＣ硬度は、基材と研磨部とを積層した後の研磨パッドの状態で測定されており、ガラス素板の表面に実際に接触されることとなる研磨部のみの状態で測定された値ではない。つまり、アスカーＣ硬度を基準に選択された研磨パッドは、その研磨部の経時変化まで考慮されてはいない。従って、アスカーＣ硬度を基準に選択された研磨パッドによれば、研磨部の経時変化により、製造されたガラス基板の品質が安定しなかったり、研磨パッドを頻繁に交換しなければならなくなったり等の不具合を発生させるおそれがあった。そして、このような不具合が発生するおそれがあることから、ガラス基板を安定した品質で歩留まりを維持しつつ、その生産量を向上させることが難しいという問題があった。
【０００６】
この発明は、このような従来技術に存在する問題点に着目してなされたものである。その目的とするところは、安定した品質で歩留まりを維持しつつ、情報記録媒体用ガラス基板の生産量の向上を図ることができる研磨パッド及びそれを使用した情報記録媒体用ガラス基板の製造方法を提供することにある。その他の目的とするところは、歩留まりを維持しつつ、安定した品質の情報記録媒体用ガラス基板を提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、請求項１に記載の研磨パッドの発明は、粗研磨されたガラス素板の表面を精密研磨して情報記録媒体用ガラス基板を製造するために使用される研磨パッドであって、基材と、同基材の表面に積層されて研磨時にはガラス素板の表面に接触する研磨部とを備え、同研磨部をＪＩＳ Ｋ７１１３に規定される１００％モジュラスが１１．８ＭＰａ以下の合成樹脂を材料とする発泡体で形成し、かつ当該研磨部の表面のＪＩＳ Ｂ０６０１−１９８２に規定される最大高さ（Ｒｍａｘ）が７０μｍ以下であることを特徴とするものである。
【０００８】
請求項２に記載の情報記録媒体用ガラス基板の製造方法の発明は、請求項１に記載の研磨パッドを使用した情報記録媒体用ガラス基板の製造方法であって、粗研磨されたガラス素板の表面に対し、３５〜７０ｇｆ／ｃｍ２の荷重で前記研磨パッドを接触させ、同荷重（ｇｆ／ｃｍ２）との積が１６０以上になるような研磨時間（分）で精密研磨を行うことを特徴とするものである。
【０００９】
請求項３に記載の情報記録媒体用ガラス基板の製造方法の発明は、請求項２に記載の発明において、前記研磨パッドは、２５〜４５ｇｆ／ｃｍ２の荷重で１０〜４０分間のドレッシング処理を行った後、前記精密研磨で繰り返して使用することを特徴とするものである。
【００１０】
請求項４に記載の情報記録媒体用ガラス基板の発明は、請求項２又は請求項３に記載の製造方法で得られた情報記録媒体用ガラス基板であって、三次元表面構造解析顕微鏡を用い、測定波長（λ）を０．１８〜０．４０ｍｍに設定して測定された表面の微小うねりの高さが０．３ｎｍ以下であることを特徴とするものである。
【００１１】
【発明の実施の形態】
以下、この発明の実施形態を、図面に基づいて詳細に説明する。
情報記録媒体用ガラス基板は、中心に円孔を有した円盤状をなし、磁気ディスク、光磁気ディスク、光ディスク等の情報記録媒体の基板として用いられている。このガラス基板を形成する材料としてはフロート法、ダウンドロー法、リドロー法又はプレス法で製造されたソーダライムガラス、アルミノシリケートガラス、ボロシリケートガラス、結晶化ガラス等が挙げられる。そして、ガラス基板の表面に磁性膜等を積層することにより、情報記録媒体が構成されるとともに、磁性膜等が積層された状態の表面が情報記録媒体の情報記録部とされる。
【００１２】
上記の情報記録媒体は、情報記録部と情報記録媒体に記録された情報を読み取るためのヘッドとの距離を狭めることにより、高密度記録化が図られている。情報記録部とヘッドとの距離を狭める場合、ガラス基板の表面に凹凸が存在すると情報記録部にも凹凸が形成されてしまう。すると、この凹凸にヘッドが接触又は干渉し、記録された情報を正確に読み取ることができなかったり、ヘッドが破損したり、情報記録部が傷ついたり等のような不具合を起こすおそれがある。そこで、ガラス基板は、その材料であるガラス素板に高精度な研磨処理を施し、その表面を研磨して平滑面とすることにより、凹凸の発生が抑えられている。
【００１３】
ここで、ガラス基板の表面の凹凸について説明する。ガラス基板の表面の状態を実際に測定すると、使用したガラス素板の歪み、撓み、反り、研磨時の機械的歪みや研磨応力等により、表面にはうねりが発生しており、また当該うねり上には微小うねりが発生している。さらに、ガラス基板の表面には、うねり及び微小うねり以外にも微小な凹凸が発生している。これらうねり、微小うねり及び微小な凹凸により、ガラス基板の表面には様々な大きさの凹凸が存在している。
【００１４】
そこで、これ以降は、ガラス基板の表面の凹凸のうち、ＪＩＳ Ｂ０６０１−１９９４に規定され、具体的には原子間力顕微鏡（ＡＦＭ）で測定された凹凸を、算術平均粗さ（Ｒａ）とする。さらに、フェイズ・シフトテクノロジー社製の多機能ディスク用干渉計（ＯＰＴＩＦＬＡＴ）を用い、測定波長（λ）を０．４〜５．０ｍｍとして表面の所定領域を白色光で走査して測定された凹凸を、うねり（Ｗａ）とする。また、Ｚｙｇｏ社製の三次元表面構造解析顕微鏡（ＮｅｗＶｉｅｗ２００）を用い、測定波長（λ）を０．１８〜０．４０ｍｍとして表面の所定領域を白色光で走査して測定された凹凸を、微小うねり（ＮＲａ）とする。
【００１５】
当該ガラス基板において、Ｒａは０．４ｎｍ以下であることが好ましい。Ｒａが０．４ｎｍより大きいと、多数の凹凸が発生し、表面が荒れ、ヘッドの移動が不安定となり、前に挙げたような不具合を起こしてしまう。また、Ｒａが０．４ｎｍ以下であればガラス基板は十分に高品質であるが、さらなる高密度記録化を図るにはＲａがより小さいものが好ましい。このことから、Ｒａは、より好ましくは０．２ｎｍ未満である。Ｗａは０．８ｎｍ以下であることが好ましい。Ｗａが０．８ｎｍより高くなると、うねりが大きくなることに伴って微小うねりまで大きくなり、ガラス基板の表面をヘッドが安定して移動することができなくなるおそれがある。また、Ｗａが０．８ｎｍ以下であればガラス基板は十分に高品質であるが、さらに高品質なガラス基板が求められる場合にはＷａがより小さいものが好ましい。このことから、Ｗａは、より好ましくは０．５ｎｍ以下であり、さらに好ましくは０．４ｎｍ以下である。
【００１６】
ＮＲａは、０．３ｎｍ以下であることが好ましい。ＮＲａが０．３ｎｍより高くなると、微小うねりが大きくなることにより、微小うねりへのヘッドの衝突又は干渉による不具合が高い割合で発生するおそれがある。また、ＮＲａが０．３ｎｍ以下であればガラス基板は十分に高品質であるが、さらに高品質なガラス基板が求められる場合にはＮＲａがより小さいものが好ましい。このことから、ＮＲａは、より好ましくは０．２ｎｍ以下である。そして、Ｒａ、Ｗａ及びＮＲａのそれぞれの値が上記の範囲を満たすよう構成されたガラス基板は、その表面からのヘッドの浮上高さ（以後、ＨＴＯと略称する）が、好ましくは４．５ｎｍ以下である。ＨＴＯが４．５ｎｍより高いと高記録密度化を図りにくくなる。ＨＴＯの下限は特に規定されないが、ＨＴＯはより低いものが好ましいことから０ｎｍである。
【００１７】
次いで、前記ガラス基板の製造方法について説明する。
ガラス基板は、シート状のガラス板から円盤状のガラス素板を切り出し、その外径寸法及び内径寸法を所定長さとした後、ガラス素板の表面に多段階に分けて研磨処理を行うことで製造される。この研磨処理は、大きく２段階の研磨工程に分けられ、各研磨工程では複数枚のガラス素板を一度に研磨するバッチ方式の研磨装置をそれぞれ使用して研磨が行われる。
【００１８】
ここで、バッチ方式の研磨装置の構成について説明する。
図２に示すように、研磨装置４１は、互いに平行となるように上下に配設された円盤状をなす上定盤４２ｂ及び下定盤４２ａと、これら上定盤４２ｂ及び下定盤４２ａを内側に囲い込むように配設された円環状をなすインターナルギヤ４３とを備えている。当該下定盤４２ａの中心には回転軸４４が突設されるとともに、同回転軸４４の下端外周面上には太陽ギヤ４５が配設されている。上定盤４２ｂの中心には挿通孔４６が透設されており、同挿通孔４６には回転軸４４が挿通されている。そして、上定盤４２ｂ、下定盤４２ａ、インターナルギヤ４３及び太陽ギヤ４５は、モータ等によりそれぞれ独立して回転することができるように駆動されている。
【００１９】
下定盤４２ａ及び上定盤４２ｂの間にはこれらに挟み込まれるようにして複数のキャリア４７が配設されている。同キャリア４７には複数の円孔４８が透設され、各円孔４８内にはガラス素板３１が収容されている。また、各キャリア４７の外周縁部にはギア４９が突設されており、各キャリア４７のギア４９は前記インターナルギヤ４３及び太陽ギヤ４５にぞれぞれ噛合されている。
【００２０】
研磨処理時において、当該研磨装置４１は、各キャリア４７内に複数枚のガラス素板３１を収容した状態で下定盤４２ａ及び上定盤４２ｂの間にキャリア４７を挟み込む。その後、下定盤４２ａ及び上定盤４２ｂとガラス素板３１との間に研磨剤を供給しながら上定盤４２ｂ、下定盤４２ａ、インターナルギヤ４３及び太陽ギヤ４５をそれぞれ回転させる。すると、下定盤４２ａ及び上定盤４２ｂの間で各キャリア４７がガラス素板３１を下定盤４２ａ及び上定盤４２ｂに接触させた状態でそれぞれ自転しながら回転軸４４を中心に公転されることにより、ガラス素板３１の基板表面が研磨される。
【００２１】
さて、ガラス素板は、まず研磨処理の１段階目の研磨工程で上記の研磨装置を使用し、その表面が粗研磨される。この１段階目の研磨工程で研磨装置の下定盤４２ａ及び上定盤４２ｂの表面には、研磨パッドとして硬質パッドがそれぞれ貼着され、同硬質パッドをガラス素板の表面に摺接させることにより、ガラス素板が粗研磨される。そして、粗研磨されたガラス素板は、所定の厚みとされるとともに、うねり、欠け（チッピング）、ひび（クラック）等の大きな欠陥等を取り除かれることにより、表面状態がある程度良好なものとされる。
【００２２】
１段階目の研磨工程では、その研磨剤として平均粒径１．２μｍ前後の粒子を溶媒としての水に分散させてスラリー状としたものが使用される。該粒子としては、アルミナ砥粒、酸化セリウムや酸化ランタン等の希土類酸化物、酸化ジルコニウム、二酸化マンガン、酸化アルミニウム、コロイダルシリカ等が挙げられる。これらのうち、希土類酸化物は研磨効率が優れていることから好ましく、希土類酸化物のなかでも酸化セリウムがより好ましい。これは、酸化セリウムはガラス材料に対して化学的に作用し、その表面をより効果的かつ効率よく研磨することが可能なためである。
【００２３】
前記硬質パッドは、ＪＩＳ Ｋ６３０１に規定される硬度（ＪＩＳ Ａ）が６５〜８５、圧縮弾性率が６０〜６５％の合成樹脂製の発泡体で形成され、圧縮率が２〜４％となるように下定盤４２ａ及び上定盤４２ｂの表面に貼着される。硬度が６５未満、圧縮弾性率が６５％より高い又は圧縮率が４％より高い場合、研磨時に硬質パッドが変形し、ガラス基板の表面にうねりが形成されてしまうおそれがある。また、硬度（ＪＩＳ Ａ）が８５より大きい、圧縮弾性率が６０％未満又は圧縮率が２％未満の場合、同硬質パッドによりガラス素板の表面が傷つき、却って表面状態が荒れてしまうおそれがある。
【００２４】
１段階目の研磨工程における研磨量は、好ましくは３０〜４０μｍである。研磨量が３０μｍ未満では表面状態を良好なものとすることができなくなる可能性がある。一方、４０μｍを超えて研磨してもそれ以上表面状態を良好なものとすることはできず、却って研磨時間が長くなることで生産効率の低下を招くおそれがある。
【００２５】
上記のようにして１段階目の研磨工程を経たガラス素板は、研磨処理の最終段階である２段階目の研磨工程でその表面が精密研磨される。この２段階目の研磨工程で研磨装置の下定盤４２ａ及び上定盤４２ｂの表面には、研磨パッドとして軟質パッドがそれぞれ貼着され、同軟質パッドをガラス素板の表面に摺接させることにより、ガラス素板が精密研磨される。精密研磨されたガラス素板は、粗研磨では取り除くことができなかったうねり、微小うねり等の欠陥の他、粗研磨時にガラス素板の表面に残留する研磨応力、粗研磨時に形成された研磨痕等を取り除かれることにより、表面状態が良好なものとされる。そして、２段階目の研磨工程を経たガラス素板に対し、最後に洗浄処理が施されることにより、ガラス素板の表面に付着した研磨粉、研磨剤、粉塵等の付着物が除去され、ガラス基板が製造される。
【００２６】
前記精密研磨では、平均粒径０．６μｍ前後（０．６±０．１μｍの範囲内）の粒子を溶媒としての水に分散させてスラリー状にした研磨剤が用いられる。該粒子としては、酸化セリウムや酸化ランタン等の希土類酸化物、酸化ジルコニウム、二酸化マンガン、酸化アルミニウム、コロイダルシリカ等が挙げられる。これらのうち、希土類酸化物である酸化セリウム及びコロイダルシリカは、研磨効率が優れていることから精密研磨で使用する研磨剤の粒子としてより好ましい。
【００２７】
軟質パッドは、ＳＲＩＳ−０１０１に規定される硬度（アスカーＣ）が５８〜７８、圧縮弾性率が５８〜７８％の合成樹脂製の発泡体を含み、圧縮率が１〜５％となるようにして用いられる。アスカーＣが５８未満、圧縮弾性率が７８％より高い又は圧縮率が５％より高い場合、研磨時に軟質パッドが変形し、製造されたガラス基板の表面に微小うねりが形成されてしまうおそれがある。また、アスカーＣが７８より大きい、圧縮弾性率が５８％未満又は圧縮率が１％未満の場合、同軟質パッドによりガラス基板の表面が傷つき、却って表面状態が荒れてしまうおそれがある。
【００２８】
精密研磨時における研磨量は好ましくは０．５〜１０μｍである。研磨量が０．５μｍ未満ではうねり、微小うねり、研磨応力、研磨痕等を十分に取り除くことができず、これに加えて、ガラス素板の表面状態を良好なものとすることができなくなるおそれがある。一方、１０μｍを超えて研磨してもそれ以上表面状態は良好なものとならず、却って研磨時間が長くなることで生産効率の低下を招くおそれがある。
【００２９】
ここで、前記軟質パッドについてより詳しく説明する。
図１に示すように、軟質パッド２０を構成する基材２１は、合成樹脂製の不織布より形成され、その表面には合成樹脂製の発泡体よりなる研磨部２２が積層されている。また、基材２１の裏面には基材２１側から順番にプライマ２３及び粘着部２４が積層されている。これら、基材２１、研磨部２２、プライマ２３及び粘着部２４から、軟質パッド２０が構成されている。
【００３０】
前記研磨部２２は、合成樹脂製の発泡体より形成されていることから、その表面にはナップ２５と称される孔を複数有している。精密研磨時には、研磨部２２の表面とキャリア４７に収容保持されたガラス素板３１の表面との間に前記研磨剤が供給される。そして、研磨剤の粒子がナップ２５内に入り込み、研磨部２２の表面と研磨剤の粒子とでガラス素板３１の表面が擦られることにより、ガラス素板３１の表面が研磨される。
【００３１】
前記プライマ２３は、基材２１の裏面にコーティング剤を塗布し、これを硬化させることによって形成され、軟質パッド２０の形状を整え、かつ維持するために設けられる。このようなコーティング剤としては、合成樹脂製のエマルジョン、エラストマー、ラテックス等が挙げられ、いずれを選択してもよい。前記粘着部２４は、軟質パッド２０を下定盤４２ａ又は上定盤４２ｂに貼着するために設けられる。この粘着部２４は、ゴム系、アクリル系等の感圧接着剤より形成されるとともに、同感圧接着剤としては、基材を有しないもの、又は伸びのある基材を有するもののいずれを使用してもよい。
【００３２】
上記の精密研磨時において、ガラス素板３１を収容保持するキャリア４７のギア４９は、インターナルギヤ４３及び太陽ギヤ４５にぞれぞれ噛合されていることから、その周縁部には経時変化により、かえりと称される突起４９ａが形成される。同突起４９ａは、研磨時に研磨部２２の表面を傷つけるため、その傷により研磨部２２の表面が毛羽立ち、凹凸が発生してしまう。研磨部２２の表面にこのような凹凸が発生した場合、同凹凸により研磨時のガラス素板３１が傷つき、製造されるガラス基板の表面に微小うねり等の欠陥が形成されるおそれがある。
【００３３】
従って、通常は製造されるガラス基板にこのような欠陥が高い割合で形成されるようになったとき、当該軟質パッド２０が耐用限界とみなされ、新たな軟質パッド２０に交換される。しかし、研磨部２２の表面の凹凸は、使用状況によってはガラス素板３１の表面を研磨するときに削り取られる可能性があり、このような場合には欠陥のないガラス基板が製造されてしまう。つまり、複数枚のガラス素板３１を研磨する各バッチ毎で、製造されるガラス基板の品質が安定せず、所望とする歩留まりを満たすことができなくなるおそれがある。
【００３４】
このような突起４９ａによって形成された研磨部２２の表面の凹凸による不具合の発生を防止するため、研磨部２２は、ＪＩＳ Ｋ７１１３に規定される１００％モジュラスが１１．８ＭＰａ（１２０ｋｇｆ／ｃｍ２）以下の合成樹脂がその材料に使用されている。なお、従来の研磨パッドである軟質パッドの材料には、１００％モジュラスが１２．３〜１３．７ＭＰａ（１２５〜１４０ｋｇｆ／ｃｍ２）の合成樹脂が主に使用されている。
【００３５】
ここで、１００％モジュラスは、前に挙げたアスカーＣのように発泡体の状態で測定された硬度とは異なり、発泡体の材料となる合成樹脂そのものの硬さを示す値である。この１００％モジュラスの値が高いものほど硬い合成樹脂であり、値が低いものほど軟らかい合成樹脂であることを示す。上記のように突起４９ａによって研磨部２２の表面が傷つくか否かは、研磨部２２の全体の硬さよりも、研磨部２２そのものの硬さ、つまり材料である合成樹脂の硬さに影響されると推測される。これは、突起４９ａが微小なものであり、同突起４９ａによる傷つきは、発泡体の硬さに影響される内奥まで達することはなく、むしろ発泡体の硬さに影響されることのない研磨部２２の表面から極僅かな範囲内で留まるためである。
【００３６】
そして、当該研磨部２２は、通常よりも１００％モジュラスの値が低く、軟らかい合成樹脂を材料として使用することにより、突起４９ａの接触時にこれを受け流し、傷つきを防止することができるように構成されている。この１００％モジュラスの値が１１．８ＭＰａよりも高い場合、突起４９ａの接触時にこれを受け流すことができず、研磨部２２の表面に傷つきが発生して製造されるガラス基板の品質が低下してしまう。
【００３７】
研磨部２２の表面の傷つきを防止するためには１００％モジュラスの値は低いものほど好ましいが、１００％モジュラスの値が過剰に低いとガラス素板３１の表面を十分に研磨することができなくなる可能性がある。従って、研磨部２２に使用する合成樹脂の１００％モジュラスの値は、好ましくは６．８〜１１．８ＭＰａ（７０〜１２０ｋｇｆ／ｃｍ２）である。また、１００％モジュラスが１１．８ＭＰａ以下の合成樹脂よりなる研磨部２２で構成された軟質パッド２０は、その耐用限界までの時間、つまり耐用時間を延ばすことが可能である。これは、研磨部２２の表面における凹凸の発生が抑制されるため、その分、製造されるガラス基板の表面にも欠陥が形成されにくくなることに由来する。
【００３８】
加えて、当該軟質パッド２０を使用して研磨を行う場合、ガラス素板３１の表面に対する軟質パッド２０の荷重は、好ましくは３５〜７０ｇｆ／ｃｍ２（３．４〜６．９ｋＰａ）である。荷重が３５ｇｆ／ｃｍ２未満の場合、ガラス素板３１を十分に研磨することができないおそれがあり、７０ｇｆ／ｃｍ２より高くすると製造されるガラス基板の表面に微小うねり等の欠陥が形成されてしまうおそれがある。
【００３９】
さらに、軟質パッド２０の荷重を上記のような範囲とする場合、その研磨時間（分）は、荷重（ｇｆ／ｃｍ２）との積が１６０以上になるように設定することが好ましい。なお、研磨時間（分）は、荷重（ｋＰａ）との積ならば、１５．５以上になるように設定することが好ましい。具体的に研磨時間は、好ましくは４分以上である。研磨時間と荷重との積が１６０未満又は研磨時間を４分未満とした場合、ガラス素板３１を十分に研磨することができないおそれがある。研磨時間の上限は特に限定されないが、過剰に長くしてもそれ以上品質は向上せず、却って生産量の低下を招くおそれもある。このため、研磨時間は、より好ましくは４分以上で１０分未満である。
【００４０】
また、当該軟質パッド２０は、実際にガラス素板３１を各バッチ毎に繰り返し精密研磨する前に、予めドレッシング処理を行うことが好ましい。このドレッシング処理とは、ドレッシング装置を使用し、軟質パッド２０の表面、つまり研磨部２２の表面を研磨することにより、表面状態を良好なものとする処理である。そして、ドレッシング処理を行うことにより、研磨部２２の表面は、ＪＩＳ Ｂ０６０１−１９８２に規定される最大高さ（Ｒｍａｘ）が７０μｍ以下とされる。Ｒｍａｘが７０μｍより大きい場合、研磨部２２の表面に特に大きな凸部が突出して形成されてしまい、同凸部により研磨されたガラス素板３１の表面が荒れてしまう。加えて、ドレッシング処理は、２５〜４５ｇｆ／ｃｍ２（２．４〜４．４ｋＰａ）の荷重で１０〜４０分間行うことが好ましい。荷重を２５ｇｆ／ｃｍ２未満、又は処理時間を１０分未満とした場合、Ｒｍａｘを７０μｍ以下とすることができなくなるおそれがある。荷重を４５ｇｆ／ｃｍ２より高く、又は処理時間を４０分より長くしても研磨部２２の表面状態はこれ以上良好なものとはならず、却って研磨部２２の表面が傷ついてしまうおそれがある。
【００４１】
前記実施形態によって発揮される効果について、以下に記載する。
・ 実施形態の情報記録媒体用ガラス基板は、１段階目の研磨工程で硬質パッドを使用してガラス素板３１の表面を粗研磨した後、２段階目の研磨工程で研磨パッドとして軟質パッド２０を使用してガラス素板３１の表面を精密研磨することにより製造される。当該軟質パッド２０は、ガラス素板３１の表面に接触する研磨部２２がＪＩＳ Ｋ７１１３に規定される１００％モジュラスが１１．８ＭＰａ以下の合成樹脂を材料に使用して形成されている。つまり、研磨部２２の材料に使用される合成樹脂は、通常のものより軟らかく、研磨時にキャリア４７のギア４９に形成された突起４９ａが接触してもこれを受け流すことができ、同突起４９ａによる傷つきの発生が抑制されている。
【００４２】
・ また、同軟質パッド２０によれば、長時間にわたって傷つきの発生が抑制されることから、製造されるガラス基板の表面にも欠陥が形成されにくく、耐用時間を延ばすことが可能である。さらに、ガラス基板を安定した品質で製造することが可能である。
【００４３】
・ また、軟質パッド２０は、予めドレッシング処理が行われることにより、その表面のＲｍａｘが７０μｍ以下とされている。つまり、研磨部２２の表面は大きな凸部等が発生しておらず、良好な表面状態となっている。
【００４４】
・ 従って、上記の各効果から、当該軟質パッド２０及び同軟質パッド２０を使用したガラス基板の製造方法によれば、安定した品質で歩留まりを維持しつつ、情報記録媒体用ガラス基板の生産量の向上を図ることができる。さらに、製造されたガラス基板は、歩留まりを維持しつつ、安定した品質のものとすることができる。
【００４５】
【実施例】
以下、前記実施形態をさらに具体化した実施例及び比較例について説明する。
（実施例１）
１００％モジュラスが８．８３ＭＰａ（９０ｋｇｆ／ｃｍ２）のポリウレタンで研磨部２２を形成し、軟質パッド２０を作製して実施例１の試料である研磨パッドを得た。次に、同軟質パッド２０をドレッシング処理し、研磨部２２の表面のＲａを７μｍ以下、Ｒｍａｘを６０μｍ以下とした。なお、１００％モジュラスは、オートグラフを使用し、ポリウレタン製の試験片を常温で測定前の長さから１００％伸ばしたとき、その強度を測定し、同強度をそのときの断面積で除することにより算出した。また、研磨部２２の表面のＲａ及びＲｍａｘは、小坂研究所製のＳＥ３４００を使用し、触針径２０μｍφ、測定長さ２５ｍｍ、測定スピード０．１ｍｍ／秒、カットオフ値０．８ｍｍに設定して測定した。
【００４６】
次いで、当該軟質パッド２０を使用し、コロイダルシリカを粒子として含む研磨剤（フジミインコーポレーテッド社製のコンポール）で複数枚のガラス素板３１の表面を研磨してガラス基板を製造した。このときのガラス素板３１は、アルミノシリケートガラスよりなり、そのサイズが、厚み０．６５ｍｍ、外径６５ｍｍ、内径２０ｍｍであった。また、このときの研磨は、軟質パッド２０のガラス素板３１に対する荷重を３５ｇｆ／ｃｍ２（３．４ｋＰａ）とし、研磨時間を荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積が３００として設定した。このとき得られた各ガラス基板について、Ｚｙｇｏ社製のＮｅｗＶｉｅｗ２００を用い、そのＮＲａを測定したところ、ＮＲａの平均値が０．２５ｎｍであり、その標準偏差が０．０５であった。そして、軟質パッド２０の耐用時間を測定したところ、２００時間であった。
【００４７】
（実施例２）
１００％モジュラスが１１．８ＭＰａのポリウレタンで研磨部２２を形成し、軟質パッド２０を作製して実施例２の試料である研磨パッドを得た。この後、ドレッシング処理を行わずにＲａ及びＲｍａｘを実施例１と同値とし、同軟質パッド２０を使用して実施例１と同様に複数枚のガラス素板３１の表面を研磨してガラス基板を製造した。このとき、軟質パッド２０のガラス素板３１に対する荷重及び荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積は実施例１と同じ値に設定した。このとき得られた各ガラス基板は、ＮＲａの平均値が０．２５ｎｍであり、その標準偏差が０．０５であった。そして、軟質パッド２０の耐用時間を測定したところ、１２５時間であった。
【００４８】
（実施例３）
１００％モジュラスが１１．８ＭＰａのポリウレタンで研磨部２２を形成し、軟質パッド２０を作製して実施例３の試料である研磨パッドを得た。この後、ドレッシング処理を行ってＲａ及びＲｍａｘを実施例１と同値とし、同軟質パッド２０を使用して実施例１と同様に複数枚のガラス素板３１の表面を研磨してガラス基板を製造した。得られた各ガラス基板は、ＮＲａの平均値が０．２０ｎｍであり、その標準偏差が０．０５であった。このとき、軟質パッド２０のガラス素板３１に対する荷重及び荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積は実施例１と同じ値に設定した。そして、軟質パッド２０の耐用時間を測定したところ、１２５時間であった。
【００４９】
（実施例４）
１００％モジュラスが１１．８ＭＰａのポリウレタンで研磨部２２を形成し、軟質パッド２０を作製して実施例４の試料である研磨パッドを得た。この後、ドレッシング処理を行ってＲａ及びＲｍａｘを実施例１と同値とし、同軟質パッド２０を使用して実施例１と同様に複数枚のガラス素板３１の表面を研磨してガラス基板を製造した。得られた各ガラス基板は、ＮＲａの平均値が０．２５ｎｍであり、その標準偏差が０．０３であった。このとき、軟質パッド２０のガラス素板３１に対する荷重を５５ｇｆ／ｃｍ２（５．４ｋＰａ）とし、荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積が４７２となるように研磨時間を設定した。そして、軟質パッド２０の耐用時間を測定したところ、１２５時間であった。
【００５０】
（比較例１）
１００％モジュラスが１２．７ＭＰａ（１３０ｋｇｆ／ｃｍ２）のポリウレタンで研磨部２２を形成し、軟質パッド２０を作製して比較例１の試料である研磨パッドを得た。この後、ドレッシング処理を行わずに研磨部２２の表面のＲａを７μｍ以下、Ｒｍａｘを５０μｍ以下とした。そして、同軟質パッド２０を使用して実施例１と同様に複数枚のガラス素板３１の表面を研磨してガラス基板を製造した。得られた各ガラス基板は、ＮＲａの平均値が０．２０ｎｍであり、その標準偏差が０．０５であった。このとき、軟質パッド２０のガラス素板３１に対する荷重及び荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積は実施例１と同じ値に設定した。そして、軟質パッド２０の耐用時間を測定したところ、５０時間であった。
【００５１】
上記の実施例１と実施例２〜４及び比較例１を比較した結果、ドレッシング処理の有無に係わらず、１００％モジュラスが低いものは耐用時間が長くなることが示された。つまり、各ガラス基板を、ＮＲａの平均値が０．２５ｎｍ以下、その標準偏差が０．０５以下となるように製造する場合、耐用時間は比較例１が５０時間と最も短く、実施例１と実施例２〜４はその２倍以上となり、耐用時間が長くなることが示された。
【００５２】
また、実施例２及び３を比較した結果、ドレッシング処理をした実施例３は、得られた各ガラス基板のＮＲａの平均値が実施例２よりも小さく、ドレッシング処理を施すことによってより品質の高いガラス基板が得られることが示された。さらに、実施例３及び４を比較した結果、軟質パッド２０のガラス素板３１に対する荷重又は荷重（ｇｆ／ｃｍ２）と研磨時間（分）との積を高めることにより、得られたガラス基板の標準偏差が小さくなることから、より品質の安定したガラス基板が得られることが示された。
【００５３】
なお、本実施形態は、次のように変更して具体化することも可能である。
・ 研磨処理は大きく２段階の工程に分けることに限らず、３段階以上の工程に分けて行ってもよい。このように構成した場合、後段階の工程でより高精度な研磨を行うことにより、さらに品質の高いガラス基板を得ることができる。
【００５４】
・ 情報記録媒体として要求される耐衝撃性、耐振動性、耐熱性等を満たすため、研磨後のガラス素板に化学強化処理を施してもよい。この化学強化処理とは、ガラス基板の組成中に含まれるリチウムイオンやナトリウムイオン等の一価の金属イオンを、これと比較してそのイオン半径が大きなナトリウムイオンやカリウムイオン等の一価の金属イオンにイオン交換することをいう。そして、ガラス基板の表面に圧縮応力を作用させて化学強化する方法である。この化学強化処理は、化学強化塩を加熱溶融した化学強化処理液にガラス基板を所定時間浸漬することによって行われる。
【００５５】
・ 実施形態では、研磨処理をバッチ方式の研磨機を使用して行ったが、これに限らず、ガラス基板を一枚ずつ研磨する枚葉方式の研磨機を使用して行ってもよい。
【００５６】
・ 各実施例では研磨部２２をポリウレタンの発泡体で形成したが１００％モジュラスが１１．８ＭＰａ（１２０ｋｇｆ／ｃｍ２）以下であれば、例えばオレフィン系樹脂、アクリル系樹脂等のような合成樹脂製の発泡体を使用してもよい。
【００５７】
さらに、前記実施形態より把握できる技術的思想について以下に記載する。
・ 前記研磨部の耐久限界までの時間が１２５時間以上であることを特徴とする請求項１に記載の研磨パッド。このように構成した場合、より長時間、安定した品質の情報記録媒体用ガラス基板を製造することができる。
【００５８】
・ 前記研磨部の表面のＪＩＳ Ｂ０６０１−１９８２に規定される表面粗さ（Ｒａ）が７μｍ以下であることを特徴とする研磨パッド。このように構成した場合、より品質の高い情報記録媒体用ガラス基板を製造することができる。
【００５９】
【発明の効果】
以上詳述したように、この発明によれば、次のような効果を奏する。
請求項１又は請求項２に記載の発明によれば、安定した品質で歩留まりを維持しつつ、情報記録媒体用ガラス基板の生産量の向上を図ることができる。
【００６０】
請求項３に記載の発明によれば、より品質の高い情報記録媒体用ガラス基板を、安定して歩留まりよく製造することができる。
請求項４に記載の発明によれば、歩留まりを維持しつつ、安定した品質のものとすることができる。
【図面の簡単な説明】
【図１】軟質パッドを示す一部を拡大した断面図。
【図２】バッチ式の研磨機を示す一部を破断した斜視図。
【符号の説明】
２０…研磨パッドとしての軟質パッド、２１…基材、２２…研磨部、３１…ガラス素板。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing pad used when manufacturing an information recording medium such as a magnetic disk, a magneto-optical disk, or an optical disk, which is a magnetic recording medium of an information recording device such as a hard disk, and a glass substrate for the information recording medium using the polishing pad. And a glass substrate for an information recording medium obtained by the method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a magnetic disk, which is one of the information recording media as described above, is used in a hard disk device or the like. The magnetic disk is manufactured by laminating a magnetic layer or the like on the surface of a glass substrate for an information recording medium (hereinafter, also abbreviated as “glass substrate”). A magnetic head for reading magnetic recording information recorded on the magnetic disk (hereinafter, also referred to as "head" for short) is configured to move while floating above the surface of the magnetic disk. I have.
[0003]
If irregularities are present on the surface of the magnetic disk when the head moves, these irregularities may collide with the head, causing problems such as damage to the head and damage to the magnetic disk. Furthermore, in recent years, the recording capacity of magnetic disks has been required to be increased. To meet this requirement, it is necessary to increase the recording density by reducing the distance between the surface of the magnetic disk and the head as much as possible. Therefore, a glass substrate used for a magnetic disk is polished at the time of manufacture, and attempts have been made to improve the flatness of the surface and to suppress the occurrence of surface irregularities. (For example, refer to Patent Document 1). In the polishing process, a polishing apparatus including a polishing carrier and a polishing pad is used. During the polishing process, the polishing pad is brought into contact with the surface of the glass substrate in a state where the glass substrate is housed in the polishing carrier, and the glass substrate and the polishing pad are rotated with respect to each other, whereby the surface of the glass substrate is polished.
[0004]
[Patent Document 1]
JP 2000-288922 A
[0005]
[Problems to be solved by the invention]
By the way, when the glass substrate manufactured by using the above polishing pad no longer satisfies the desired quality, the polishing pad is regarded as a durable limit and is replaced with a new polishing pad. A conventional polishing pad is selected based on Asker C hardness specified in SRIS-0101 and has a hardness corresponding to a purpose such as hardness of a polishing carrier, hardness of a glass material, and the like. The quality required for the glass substrate, the time for replacing the polishing pad, and the like have been determined. The polishing pad includes a base made of a nonwoven fabric or the like, and a polishing part formed of a synthetic resin foam laminated on the surface of the base and brought into contact with the surface of the glass substrate. However, the Asker C hardness is measured in the state of the polishing pad after laminating the base material and the polishing part, and is measured only in the state of the polishing part which is actually brought into contact with the surface of the glass plate. It is not a value. That is, the polishing pad selected on the basis of Asker C hardness does not take into account the aging of the polished portion. Therefore, according to the polishing pad selected on the basis of Asker C hardness, the quality of the manufactured glass substrate is not stable due to the aging of the polishing portion, the polishing pad must be frequently replaced, and the like. There was a risk of causing the problem described above. Since such a problem may occur, it is difficult to improve the production amount of the glass substrate while maintaining the yield with stable quality.
[0006]
The present invention has been made by paying attention to such problems existing in the related art. The purpose is to provide a polishing pad capable of improving the production amount of an information recording medium glass substrate while maintaining a yield with stable quality, and a method of manufacturing an information recording medium glass substrate using the same. To provide. Another object is to provide a glass substrate for an information recording medium having a stable quality while maintaining a yield.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention of a polishing pad according to claim 1 is a polishing pad used for manufacturing a glass substrate for an information recording medium by precisely polishing a surface of a glass substrate which has been roughly polished. A pad, comprising: a base material; and a polishing portion laminated on the surface of the base material and in contact with the surface of the glass base plate during polishing, wherein the polishing portion has a 100% modulus defined by JIS K7113. It is formed of a foam made of a synthetic resin of 8 MPa or less, and has a maximum height (Rmax) of 70 μm or less defined by JIS B0601-1982 on the surface of the polished portion.
[0008]
An invention of a method for manufacturing a glass substrate for an information recording medium according to claim 2 is a method for manufacturing a glass substrate for an information recording medium using the polishing pad according to claim 1, wherein the glass plate is roughly polished. 35 to 70 gf / cm with respect to the surface of 2 The polishing pad is brought into contact with the load (gf / cm). 2 ) Is subjected to precision polishing in a polishing time (minute) such that the product of the above is 160 or more.
[0009]
According to a third aspect of the present invention, there is provided a method of manufacturing a glass substrate for an information recording medium, wherein the polishing pad according to the second aspect is configured to have a thickness of 25 to 45 gf / cm. 2 After performing a dressing treatment for 10 to 40 minutes with a load of, the above-mentioned precision polishing is repeatedly used.
[0010]
According to a fourth aspect of the present invention, there is provided a glass substrate for an information recording medium obtained by the manufacturing method according to the second or third aspect, wherein the three-dimensional surface structure analysis microscope is used. The height of the minute waviness on the surface measured at a measurement wavelength (λ) of 0.18 to 0.40 mm is 0.3 nm or less.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
BACKGROUND ART A glass substrate for an information recording medium has a disk shape having a circular hole at the center, and is used as a substrate of an information recording medium such as a magnetic disk, a magneto-optical disk, and an optical disk. Examples of a material for forming the glass substrate include a soda lime glass, an aluminosilicate glass, a borosilicate glass, and a crystallized glass manufactured by a float method, a downdraw method, a redraw method, or a press method. Then, an information recording medium is formed by laminating a magnetic film or the like on the surface of the glass substrate, and the surface on which the magnetic film or the like is laminated serves as an information recording section of the information recording medium.
[0012]
In the above information recording medium, high-density recording is achieved by reducing the distance between an information recording section and a head for reading information recorded on the information recording medium. When the distance between the information recording section and the head is reduced, if the surface of the glass substrate has irregularities, the information recording section will also have irregularities. Then, the head comes into contact with or interferes with the unevenness, and there is a possibility that the recorded information cannot be read accurately, the head is damaged, and the information recording portion is damaged. Therefore, the occurrence of irregularities is suppressed by subjecting a glass substrate, which is a material of the glass substrate, to high-precision polishing treatment and polishing the surface to a smooth surface.
[0013]
Here, the irregularities on the surface of the glass substrate will be described. When the state of the surface of the glass substrate is actually measured, the surface of the glass plate used has undulation due to distortion, bending, warping, mechanical distortion during polishing, polishing stress, and the like. Has small undulations. Further, in addition to undulations and minute undulations, minute irregularities occur on the surface of the glass substrate. Due to these undulations, minute undulations and minute irregularities, irregularities of various sizes exist on the surface of the glass substrate.
[0014]
Therefore, hereinafter, of the irregularities on the surface of the glass substrate, the irregularities defined by JIS B0601-1994, specifically, measured by an atomic force microscope (AFM) are defined as arithmetic average roughness (Ra). . Further, using a multifunction disk interferometer (OPTIFLAT) manufactured by Phase Shift Technology, the measurement wavelength (λ) is set to 0.4 to 5.0 mm, and a predetermined area on the surface is scanned with white light to obtain the unevenness. Is referred to as swell (Wa). Further, using a three-dimensional surface structure analysis microscope (NewView 200) manufactured by Zygo, the measurement wavelength (λ) is set to 0.18 to 0.40 mm, a predetermined area of the surface is scanned with white light, and irregularities measured are minute. Swell (NRa).
[0015]
In the glass substrate, Ra is preferably 0.4 nm or less. If Ra is larger than 0.4 nm, many irregularities are generated, the surface becomes rough, the movement of the head becomes unstable, and the above-mentioned problems occur. If the Ra is 0.4 nm or less, the glass substrate has a sufficiently high quality. However, in order to achieve higher density recording, a glass substrate having a smaller Ra is preferable. For this reason, Ra is more preferably less than 0.2 nm. Wa is preferably 0.8 nm or less. If Wa is higher than 0.8 nm, the waviness increases and the waviness increases to minute waviness, and the head may not be able to stably move on the surface of the glass substrate. If the Wa is 0.8 nm or less, the glass substrate has a sufficiently high quality. However, if a higher quality glass substrate is required, a smaller Wa is preferable. From this, Wa is more preferably 0.5 nm or less, and still more preferably 0.4 nm or less.
[0016]
NRa is preferably 0.3 nm or less. If the NRa is higher than 0.3 nm, the fine waviness becomes large, and there is a possibility that a problem due to collision or interference of the head with the fine waviness occurs at a high rate. If the NRa is 0.3 nm or less, the glass substrate has a sufficiently high quality. However, if a higher quality glass substrate is required, a smaller NRa is preferable. For this reason, NRa is more preferably 0.2 nm or less. The glass substrate configured so that each value of Ra, Wa, and NRa satisfies the above range has a flying height of the head from the surface thereof (hereinafter, abbreviated as HTO) of preferably 4.5 nm or less. It is. If the HTO is higher than 4.5 nm, it is difficult to achieve a high recording density. Although the lower limit of HTO is not particularly defined, HTO is 0 nm because a lower HTO is preferable.
[0017]
Next, a method for manufacturing the glass substrate will be described.
The glass substrate is obtained by cutting a disk-shaped glass plate from a sheet-shaped glass plate, setting its outer diameter and inner diameter to a predetermined length, and then performing a polishing process on the surface of the glass plate in multiple stages. Manufactured. This polishing process is roughly divided into two stages of polishing processes, and in each polishing process, polishing is performed using a batch-type polishing apparatus for polishing a plurality of glass plates at a time.
[0018]
Here, the configuration of the batch type polishing apparatus will be described.
As shown in FIG. 2, the polishing apparatus 41 includes upper and lower platens 42 b and 42 a which are disc-shaped and arranged vertically so as to be parallel to each other, and these upper and lower platens 42 b and 42 a are arranged inside. And an annular internal gear 43 disposed so as to surround it. A rotating shaft 44 projects from the center of the lower platen 42a, and a sun gear 45 is disposed on the outer peripheral surface of the lower end of the rotating shaft 44. An insertion hole 46 is provided in the center of the upper stool 42b, and the rotation shaft 44 is inserted into the insertion hole 46. The upper surface plate 42b, the lower surface plate 42a, the internal gear 43, and the sun gear 45 are driven by a motor or the like so that they can rotate independently.
[0019]
A plurality of carriers 47 are arranged between the lower surface plate 42a and the upper surface plate 42b so as to be sandwiched therebetween. The carrier 47 is provided with a plurality of circular holes 48, and the glass plate 31 is accommodated in each circular hole 48. A gear 49 protrudes from the outer peripheral edge of each carrier 47, and the gear 49 of each carrier 47 is meshed with the internal gear 43 and the sun gear 45, respectively.
[0020]
During the polishing process, the polishing apparatus 41 sandwiches the carrier 47 between the lower lapping plate 42a and the upper lapping plate 42b in a state where a plurality of the glass base plates 31 are accommodated in each carrier 47. Thereafter, the upper platen 42b, the lower platen 42a, the internal gear 43, and the sun gear 45 are rotated while supplying an abrasive between the lower platen 42a and the upper platen 42b and the glass base plate 31, respectively. Then, each carrier 47 is revolved around the rotation shaft 44 while rotating itself in a state where the glass base plate 31 is in contact with the lower surface plate 42a and the upper surface plate 42b between the lower surface plate 42a and the upper surface plate 42b. Thereby, the substrate surface of the glass base plate 31 is polished.
[0021]
First, the surface of the glass blank is roughly polished by using the above-mentioned polishing apparatus in the first polishing step of the polishing process. In the first polishing step, hard pads are respectively attached as polishing pads to the surfaces of the lower platen 42a and the upper platen 42b of the polishing apparatus, and the hard pads are brought into sliding contact with the surface of the glass plate. Then, the glass plate is roughly polished. The coarsely polished glass plate is made to have a predetermined thickness and has a good surface condition to some extent by removing large defects such as undulation, chipping, and cracks. You.
[0022]
In the first polishing step, a slurry obtained by dispersing particles having an average particle size of about 1.2 μm in water as a solvent is used as the polishing agent. Examples of the particles include alumina abrasive grains, rare earth oxides such as cerium oxide and lanthanum oxide, zirconium oxide, manganese dioxide, aluminum oxide, and colloidal silica. Of these, rare earth oxides are preferred because of their excellent polishing efficiency, and among the rare earth oxides, cerium oxide is more preferred. This is because cerium oxide chemically acts on the glass material and can polish the surface more effectively and efficiently.
[0023]
The hard pad is formed of a synthetic resin foam having a hardness (JIS A) defined by JIS K6301 of 65 to 85 and a compression modulus of 60 to 65%, and a compression rate of 2 to 4%. Are attached to the surfaces of the lower surface plate 42a and the upper surface plate 42b. If the hardness is less than 65 and the compression modulus is higher than 65% or the compression ratio is higher than 4%, the hard pad may be deformed during polishing, and undulation may be formed on the surface of the glass substrate. When the hardness (JIS A) is greater than 85, the compression modulus is less than 60%, or the compression ratio is less than 2%, the surface of the glass plate may be damaged by the hard pad, and the surface condition may be roughened. is there.
[0024]
The polishing amount in the first polishing step is preferably 30 to 40 μm. If the polishing amount is less than 30 μm, there is a possibility that the surface state cannot be improved. On the other hand, even if it is polished beyond 40 μm, the surface condition cannot be further improved, and the polishing time may be rather long, which may cause a decrease in production efficiency.
[0025]
The surface of the glass blank that has undergone the first-stage polishing process as described above is precisely polished in the second-stage polishing process, which is the final stage of the polishing process. In the second polishing step, soft pads as polishing pads are respectively adhered to the surfaces of the lower platen 42a and the upper platen 42b of the polishing apparatus, and the soft pads are brought into sliding contact with the surface of the glass plate. Then, the glass plate is precisely polished. The precision polished glass base plate has undulations and fine undulations that could not be removed by rough polishing, polishing stress remaining on the surface of the glass base plate during rough polishing, and polishing marks formed during rough polishing. By removing the like, the surface condition is improved. Then, the glass plate that has passed through the second-stage polishing step is finally subjected to a cleaning process, whereby the adhered substances such as abrasive powder, abrasive, and dust attached to the surface of the glass plate are removed, A glass substrate is manufactured.
[0026]
In the precision polishing, a slurry is used in which particles having an average particle diameter of about 0.6 μm (within a range of 0.6 ± 0.1 μm) are dispersed in water as a solvent to form a slurry. Examples of the particles include rare earth oxides such as cerium oxide and lanthanum oxide, zirconium oxide, manganese dioxide, aluminum oxide, and colloidal silica. Among them, cerium oxide and colloidal silica, which are rare earth oxides, are more preferable as abrasive particles used in precision polishing because of their excellent polishing efficiency.
[0027]
The soft pad includes a synthetic resin foam having a hardness (Asker C) of 58 to 78 and a compression elasticity of 58 to 78% as defined in SRIS-0101, and a compression rate of 1 to 5%. Used. If Asker C is less than 58 and the compression modulus is higher than 78% or the compression ratio is higher than 5%, the soft pad may be deformed at the time of polishing, and minute undulation may be formed on the surface of the manufactured glass substrate. . When Asker C is larger than 78, the compression modulus is less than 58%, or the compression ratio is less than 1%, the surface of the glass substrate may be damaged by the soft pad, and the surface condition may be roughened.
[0028]
The polishing amount at the time of precision polishing is preferably 0.5 to 10 μm. If the polishing amount is less than 0.5 μm, undulation, minute undulation, polishing stress, polishing marks, etc. cannot be sufficiently removed, and in addition, the surface condition of the glass base plate may not be able to be improved. There is. On the other hand, even if it is polished beyond 10 μm, the surface state will not be better any more, and on the contrary, the polishing time will be prolonged, which may lead to a decrease in production efficiency.
[0029]
Here, the soft pad will be described in more detail.
As shown in FIG. 1, the base material 21 constituting the soft pad 20 is formed of a nonwoven fabric made of synthetic resin, and a polishing portion 22 made of a synthetic resin foam is laminated on the surface thereof. A primer 23 and an adhesive portion 24 are sequentially laminated on the back surface of the substrate 21 from the substrate 21 side. The soft pad 20 is composed of the substrate 21, the polishing section 22, the primer 23, and the adhesive section 24.
[0030]
Since the polishing portion 22 is formed of a synthetic resin foam, the surface thereof has a plurality of holes called naps 25 on its surface. At the time of precision polishing, the abrasive is supplied between the surface of the polishing section 22 and the surface of the glass base plate 31 held and held in the carrier 47. Then, the particles of the abrasive enter the nap 25 and the surface of the glass plate 31 is polished by rubbing the surface of the polishing portion 22 with the particles of the abrasive.
[0031]
The primer 23 is formed by applying a coating agent on the back surface of the substrate 21 and curing the coating agent, and is provided for adjusting and maintaining the shape of the soft pad 20. Examples of such a coating agent include an emulsion, an elastomer, and a latex made of a synthetic resin, and any of them may be selected. The adhesive portion 24 is provided for attaching the soft pad 20 to the lower surface plate 42a or the upper surface plate 42b. The adhesive portion 24 is formed of a pressure-sensitive adhesive such as a rubber-based or acrylic-based adhesive. As the pressure-sensitive adhesive, either a material having no base material or a material having a stretchable base material is used. You may.
[0032]
At the time of the above-mentioned precision polishing, the gear 49 of the carrier 47 for holding and holding the glass base plate 31 is meshed with the internal gear 43 and the sun gear 45, respectively. A projection 49a called a burr is formed. The projections 49a damage the surface of the polishing section 22 during polishing, and the scratches cause the surface of the polishing section 22 to fluff and generate irregularities. When such irregularities occur on the surface of the polishing section 22, the glass irregularities during polishing may be damaged by the irregularities, and defects such as minute waviness may be formed on the surface of the manufactured glass substrate.
[0033]
Therefore, when such a defect is formed at a high rate on a glass substrate which is normally manufactured, the soft pad 20 is regarded as a service limit and is replaced with a new soft pad 20. However, the irregularities on the surface of the polishing section 22 may be removed when polishing the surface of the glass base plate 31 depending on the use condition, and in such a case, a glass substrate having no defect is manufactured. That is, the quality of the glass substrate to be manufactured is not stable in each batch in which a plurality of the glass base plates 31 are polished, and the desired yield may not be satisfied.
[0034]
In order to prevent the occurrence of a defect due to the unevenness of the surface of the polishing portion 22 formed by such projections 49a, the polishing portion 22 has a 100% modulus defined by JIS K7113 of 11.8 MPa (120 kgf / cm). 2 ) The following synthetic resins are used for the material. The material of the soft pad which is a conventional polishing pad has a 100% modulus of 12.3 to 13.7 MPa (125 to 140 kgf / cm). 2 ) Is mainly used.
[0035]
Here, the 100% modulus is a value indicating the hardness of the synthetic resin itself, which is a material of the foam, different from the hardness measured in the state of the foam like Asker C described above. A higher value of the 100% modulus indicates a harder synthetic resin, and a lower value indicates a softer synthetic resin. Whether or not the projection 49a damages the surface of the polishing section 22 as described above is affected by the hardness of the polishing section 22 itself, that is, the hardness of the synthetic resin as the material, rather than the overall hardness of the polishing section 22. It is presumed. This is because the projections 49a are minute, and the scratches caused by the projections 49a do not reach the inner part affected by the hardness of the foam, but rather are polished without being affected by the hardness of the foam. This is because it stays within a very small range from the surface of the portion 22.
[0036]
The polishing portion 22 is configured to have a value of 100% modulus lower than usual and use a soft synthetic resin as a material so that when the projection 49a comes into contact with the projection 49a, the projection 49a can be prevented from being damaged. ing. If the value of the 100% modulus is higher than 11.8 MPa, the protrusions 49a cannot be passed when contacted, and the surface of the polishing portion 22 is scratched to deteriorate the quality of the manufactured glass substrate. I will.
[0037]
In order to prevent the surface of the polishing portion 22 from being damaged, it is preferable that the value of the 100% modulus is low. However, if the value of the 100% modulus is excessively low, the surface of the glass plate 31 cannot be sufficiently polished. there is a possibility. Therefore, the value of the 100% modulus of the synthetic resin used for the polishing section 22 is preferably 6.8 to 11.8 MPa (70 to 120 kgf / cm). 2 ). Further, the soft pad 20 composed of the polishing portion 22 made of a synthetic resin having a 100% modulus of 11.8 MPa or less can extend the time up to its useful limit, that is, the useful time. This is because the generation of irregularities on the surface of the polishing section 22 is suppressed, and accordingly, defects are less likely to be formed on the surface of the manufactured glass substrate.
[0038]
In addition, when polishing is performed using the soft pad 20, the load of the soft pad 20 on the surface of the glass base plate 31 is preferably 35 to 70 gf / cm. 2 (3.4 to 6.9 kPa). Load is 35gf / cm 2 If it is less than 70 gf / cm, the glass base plate 31 may not be sufficiently polished. 2 If the height is higher, defects such as minute waviness may be formed on the surface of the manufactured glass substrate.
[0039]
Further, when the load of the soft pad 20 is in the above range, the polishing time (minute) is determined by the load (gf / cm). 2 ) Is preferably set to be 160 or more. The polishing time (minutes) is preferably set to be 15.5 or more if it is a product of the load (kPa). Specifically, the polishing time is preferably 4 minutes or more. When the product of the polishing time and the load is less than 160 or the polishing time is less than 4 minutes, the glass base plate 31 may not be sufficiently polished. The upper limit of the polishing time is not particularly limited. However, if the polishing time is excessively long, the quality is not further improved, and the production amount may be reduced. Therefore, the polishing time is more preferably 4 minutes or more and less than 10 minutes.
[0040]
In addition, it is preferable that the soft pad 20 be subjected to a dressing process before actually polishing the glass plate 31 repeatedly and precisely for each batch. The dressing process is a process for improving the surface condition by polishing the surface of the soft pad 20, that is, the surface of the polishing section 22, using a dressing apparatus. Then, by performing the dressing process, the surface of the polishing section 22 has a maximum height (Rmax) defined by JIS B0601-1982 of 70 μm or less. If Rmax is larger than 70 μm, a particularly large projection is formed on the surface of the polishing section 22 so as to protrude, and the surface of the glass base plate 31 polished by the projection is roughened. In addition, the dressing process is 25-45 gf / cm 2 (2.4 to 4.4 kPa) for 10 to 40 minutes. Load 25gf / cm 2 If the processing time is shorter than 10 minutes or the processing time is shorter than 10 minutes, Rmax may not be able to be reduced to 70 μm or less. Load 45gf / cm 2 Even if the processing time is higher or the processing time is longer than 40 minutes, the surface state of the polishing section 22 will not be further improved, and the surface of the polishing section 22 may be rather damaged.
[0041]
The effects exerted by the above embodiment will be described below.
In the glass substrate for an information recording medium of the embodiment, the surface of the glass base plate 31 is roughly polished using a hard pad in the first polishing step, and then the soft pad 20 is used as a polishing pad in the second polishing step. It is manufactured by precisely polishing the surface of the glass blank 31 using The soft pad 20 is formed by using a synthetic resin having a 100% modulus of 11.8 MPa or less as defined in JIS K7113 for the polishing portion 22 that contacts the surface of the glass base plate 31 as a material. In other words, the synthetic resin used as the material of the polishing portion 22 is softer than a normal resin, and can pass through even if the projection 49a formed on the gear 49 of the carrier 47 comes into contact during polishing, and can be discharged. The occurrence of damage is suppressed.
[0042]
Also, according to the soft pad 20, since the occurrence of scratches is suppressed for a long time, defects are not easily formed on the surface of the glass substrate to be manufactured, and the service life can be extended. Further, a glass substrate can be manufactured with stable quality.
[0043]
In addition, the soft pad 20 is subjected to a dressing process in advance, so that the Rmax of the surface is set to 70 μm or less. In other words, the surface of the polishing section 22 is in a good surface state without any large projections or the like.
[0044]
Therefore, from the above effects, according to the soft pad 20 and the method for manufacturing a glass substrate using the soft pad 20, the production amount of the glass substrate for the information recording medium can be reduced while maintaining the yield with stable quality. Improvement can be achieved. Furthermore, the manufactured glass substrate can be of stable quality while maintaining the yield.
[0045]
【Example】
Hereinafter, examples and comparative examples that further embody the above embodiment will be described.
(Example 1)
The 100% modulus is 8.83 MPa (90 kgf / cm 2 The polishing portion 22 was formed with the polyurethane of (2), and the soft pad 20 was produced to obtain the polishing pad as the sample of Example 1. Next, the soft pad 20 was subjected to a dressing process so that Ra on the surface of the polishing portion 22 was 7 μm or less, and Rmax was 60 μm or less. The 100% modulus is measured by using an autograph when the polyurethane test piece is stretched 100% from the length before measurement at room temperature, and its strength is measured, and the strength is divided by the cross-sectional area at that time. It was calculated by the following. Further, Ra and Rmax of the surface of the polishing section 22 were set to a stylus diameter of 20 μmφ, a measurement length of 25 mm, a measurement speed of 0.1 mm / sec, and a cut-off value of 0.8 mm using SE3400 manufactured by Kosaka Laboratory. Measured.
[0046]
Next, using the soft pad 20, the surfaces of the plurality of glass base plates 31 were polished with an abrasive containing colloidal silica as particles (Compol made by Fujimi Incorporated) to produce a glass substrate. At this time, the glass base plate 31 was made of aluminosilicate glass, and its size was 0.65 mm in thickness, 65 mm in outer diameter, and 20 mm in inner diameter. In addition, the polishing at this time is such that the load of the soft pad 20 on the glass base plate 31 is 35 gf / cm 2 (3.4 kPa) and the polishing time is set to a load (gf / cm). 2 ) And the polishing time (min) were set to 300. The NRa of each glass substrate obtained at this time was measured using NewView200 manufactured by Zygo Co., and the average value of NRa was 0.25 nm and the standard deviation was 0.05. When the service life of the soft pad 20 was measured, it was 200 hours.
[0047]
(Example 2)
The polishing portion 22 was formed of polyurethane having a 100% modulus of 11.8 MPa, and a soft pad 20 was produced to obtain a polishing pad as a sample of Example 2. Thereafter, Ra and Rmax were set to the same values as in Example 1 without performing the dressing process, and the surfaces of the plurality of glass base plates 31 were polished using the same soft pad 20 as in Example 1 to remove the glass substrate. Manufactured. At this time, the load and load (gf / cm) of the soft pad 20 on the glass base plate 31 are set. 2 ) And the polishing time (minute) were set to the same value as in Example 1. Each of the glass substrates obtained at this time had an average value of NRa of 0.25 nm and a standard deviation of 0.05. When the service life of the soft pad 20 was measured, it was 125 hours.
[0048]
(Example 3)
The polishing portion 22 was formed of polyurethane having a 100% modulus of 11.8 MPa, and a soft pad 20 was produced to obtain a polishing pad as a sample of Example 3. Thereafter, a dressing process is performed to set Ra and Rmax to the same values as in the first embodiment, and the surfaces of a plurality of glass base plates 31 are polished using the same soft pad 20 as in the first embodiment to manufacture a glass substrate. did. Each of the obtained glass substrates had an average value of NRa of 0.20 nm and a standard deviation of 0.05. At this time, the load and load (gf / cm) of the soft pad 20 on the glass base plate 31 are set. 2 ) And the polishing time (minute) were set to the same value as in Example 1. When the service life of the soft pad 20 was measured, it was 125 hours.
[0049]
(Example 4)
The polishing portion 22 was formed of polyurethane having a 100% modulus of 11.8 MPa, and the soft pad 20 was manufactured to obtain a polishing pad as a sample of Example 4. Thereafter, a dressing process is performed to set Ra and Rmax to the same values as in the first embodiment, and the surfaces of a plurality of glass base plates 31 are polished using the same soft pad 20 as in the first embodiment to manufacture a glass substrate. did. Each of the obtained glass substrates had an average value of NRa of 0.25 nm and a standard deviation of 0.03. At this time, the load of the soft pad 20 on the glass base plate 31 was 55 gf / cm. 2 (5.4 kPa) and the load (gf / cm 2 ) And the polishing time (minutes) were set to 472. When the service life of the soft pad 20 was measured, it was 125 hours.
[0050]
(Comparative Example 1)
100% modulus is 12.7 MPa (130 kgf / cm 2 The polishing portion 22 was formed with the polyurethane of (2), and the soft pad 20 was produced to obtain a polishing pad as a sample of Comparative Example 1. Thereafter, Ra on the surface of the polishing section 22 was set to 7 μm or less and Rmax was set to 50 μm or less without performing a dressing process. Then, using the same soft pad 20, the surfaces of a plurality of glass base plates 31 were polished in the same manner as in Example 1 to produce a glass substrate. Each of the obtained glass substrates had an average value of NRa of 0.20 nm and a standard deviation of 0.05. At this time, the load and load (gf / cm) of the soft pad 20 on the glass base plate 31 are set. 2 ) And the polishing time (minute) were set to the same value as in Example 1. When the service life of the soft pad 20 was measured, it was 50 hours.
[0051]
As a result of comparing Example 1 with Examples 2 to 4 and Comparative Example 1, it was shown that those having a low 100% modulus have a long service life regardless of the presence or absence of the dressing treatment. That is, when each glass substrate is manufactured such that the average value of NRa is 0.25 nm or less and the standard deviation thereof is 0.05 or less, the durable time of Comparative Example 1 is 50 hours, which is the shortest. Examples 2 to 4 were twice or more than that, indicating that the service life was prolonged.
[0052]
Further, as a result of comparison between Examples 2 and 3, Example 3 in which the dressing process was performed had an average value of NRa of each obtained glass substrate smaller than that in Example 2, and higher quality was obtained by performing the dressing process. It was shown that a glass substrate was obtained. Furthermore, as a result of comparing Examples 3 and 4, the load or load (gf / cm) of the soft pad 20 on the glass base plate 31 was obtained. 2 ) And the polishing time (minutes), the standard deviation of the obtained glass substrate was reduced, indicating that a more stable glass substrate could be obtained.
[0053]
This embodiment can be embodied with the following modifications.
The polishing process is not limited to being roughly divided into two stages, but may be performed in three or more stages. In such a configuration, a higher-quality glass substrate can be obtained by performing higher-precision polishing in a later step.
[0054]
In order to satisfy the shock resistance, vibration resistance, heat resistance, and the like required for the information recording medium, the polished glass plate may be subjected to a chemical strengthening treatment. This chemical strengthening treatment means that monovalent metal ions such as lithium ions and sodium ions contained in the composition of the glass substrate are compared with monovalent metal ions such as sodium ions and potassium ions having a larger ion radius. Ion exchange refers to ions. In this method, a compressive stress is applied to the surface of the glass substrate to chemically strengthen the glass substrate. This chemical strengthening treatment is performed by immersing the glass substrate in a chemical strengthening treatment solution in which the chemical strengthening salt is heated and melted for a predetermined time.
[0055]
In the embodiment, the polishing process is performed using a batch-type polishing machine. However, the present invention is not limited to this. The polishing process may be performed using a single-wafer-type polishing machine for polishing glass substrates one by one.
[0056]
In each of the examples, the polishing portion 22 was formed of a polyurethane foam, but the 100% modulus was 11.8 MPa (120 kgf / cm). 2 In the following cases, for example, a foam made of a synthetic resin such as an olefin resin or an acrylic resin may be used.
[0057]
Further, technical ideas that can be grasped from the embodiment will be described below.
The polishing pad according to claim 1, wherein a time required for the polishing portion to reach a durability limit is 125 hours or more. With this configuration, it is possible to manufacture a glass substrate for an information recording medium with stable quality for a longer time.
[0058]
A polishing pad, wherein the surface of the polishing section has a surface roughness (Ra) specified in JIS B0601-1982 of 7 μm or less. With such a configuration, a glass substrate for an information recording medium with higher quality can be manufactured.
[0059]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
According to the first or second aspect of the invention, it is possible to improve the production amount of the glass substrate for the information recording medium while maintaining the yield with stable quality.
[0060]
According to the third aspect of the invention, a glass substrate for an information recording medium having higher quality can be stably manufactured with a high yield.
According to the invention described in claim 4, stable quality can be achieved while maintaining the yield.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view showing a part of a soft pad.
FIG. 2 is a partially cutaway perspective view showing a batch type polishing machine.
[Explanation of symbols]
20: a soft pad as a polishing pad, 21: a base material, 22: a polishing portion, 31: a glass plate.

Claims (4)

粗研磨されたガラス素板の表面を精密研磨して情報記録媒体用ガラス基板を製造するために使用される研磨パッドであって、
基材と、同基材の表面に積層されて研磨時にはガラス素板の表面に接触する研磨部とを備え、同研磨部をＪＩＳ Ｋ７１１３に規定される１００％モジュラスが１１．８ＭＰａ以下の合成樹脂を材料とする発泡体で形成し、かつ当該研磨部の表面のＪＩＳ Ｂ０６０１−１９８２に規定される最大高さ（Ｒｍａｘ）が７０μｍ以下であることを特徴とする研磨パッド。A polishing pad used to manufacture a glass substrate for an information recording medium by precisely polishing the surface of a roughly polished glass plate,
A base material, and a polishing portion laminated on the surface of the base material and contacting the surface of the glass plate during polishing, wherein the polishing portion is made of a synthetic resin having a 100% modulus defined by JIS K7113 of 11.8 MPa or less. A polishing pad characterized by being formed of a foam made of material, and having a maximum height (Rmax) defined by JIS B0601-1982 of the surface of the polishing portion of 70 μm or less. 請求項１に記載の研磨パッドを使用した情報記録媒体用ガラス基板の製造方法であって、
粗研磨されたガラス素板の表面に対し、３５〜７０ｇｆ／ｃｍ２の荷重で前記研磨パッドを接触させ、同荷重（ｇｆ／ｃｍ２）との積が１６０以上になるような研磨時間（分）で精密研磨を行うことを特徴とする情報記録媒体用ガラス基板の製造方法。A method for manufacturing a glass substrate for an information recording medium using the polishing pad according to claim 1,
To rough polished surface of the glass workpiece, 35～70Gf / with a load of cm 2 are brought into contact with the polishing pad, the load (gf / cm 2) the product of the is more than 160 such polishing time (min A) a method of manufacturing a glass substrate for an information recording medium, wherein the polishing is performed by precision polishing. 前記研磨パッドは、２５〜４５ｇｆ／ｃｍ２の荷重で１０〜４０分間のドレッシング処理を行った後、前記精密研磨で繰り返して使用することを特徴とする請求項２に記載の情報記録媒体用ガラス基板の製造方法。The polishing pad, 25～45Gf / after cm was carried out 2 of the dressing of 10 to 40 minutes under a load of glass for information recording medium according to claim 2, characterized in that repeated use in the precision polishing Substrate manufacturing method. 請求項２又は請求項３に記載の製造方法で得られた情報記録媒体用ガラス基板であって、
三次元表面構造解析顕微鏡を用い、測定波長（λ）を０．１８〜０．４０ｍｍに設定して測定された表面の微小うねりの高さが０．３ｎｍ以下であることを特徴とする情報記録媒体用ガラス基板。A glass substrate for an information recording medium obtained by the manufacturing method according to claim 2 or claim 3,
The information recording characterized in that the height of the minute waviness on the surface measured using a three-dimensional surface structure analysis microscope at a measurement wavelength (λ) of 0.18 to 0.40 mm is 0.3 nm or less. Glass substrate for media.
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US10/807,670 US6932677B2 (en) 2003-03-28 2004-03-24 Polishing pad, method of manufacturing glass substrate for use in data recording medium using the pad, and glass substrate for use in data recording medium obtained by using the method
US11/182,296 US7059951B2 (en) 2003-03-28 2005-07-15 Polishing pad, method of manufacturing glass substrate for use in data recording medium using the pad, and glass substrate for use in data recording medium obtained by using the method

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